How do I pass a 'null' action

Question

I have the following function definition

private void DoExport(Action<ColumnView, bool> UpdateColumns)  
{  
...  
}

private void UpdateNonPrintableColumns(ColumnView view, bool visible)  
{  
...  
}   

Example of it being called:

DoExport(UpdateNonPrintableColumns);

My question is. How do I pass a 'null' action? Is it even possible?

eg
DoExport(null); <- Throws exception

DoExport(null) causes an exception to be thrown when the action gets called in the function body

Answer 1

Pass in an empty action if you want to:

DoExport((x, y) => { })

Second, you have to review your code, since passing in null is perfectly fine.

public void X()
{
    A(null);
}

public void A(Action<ColumnView, bool> a)
{
    if (a != null)
    {
        a();
    }
}

Or as per C# 6 (using the null-propagation operator):

public void A(Action<ColumnView, bool> a)
{
    a?.Invoke();
}

Answer 2

你可以传递一个什么都不做的动作：

DoExport((_, __) => { });

Answer 3

Or just handle it inside of the method:

private void DoExport(Action<ColumnView, bool> UpdateColumns)  
{  
  if (UpdateColumns != null)
    UpdateColumns(...);
}